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7H                                           FLOUA  INBICA.
after the beginning of April, it advances rapidly into the
northern hemisphere, and two defined regions of excessive
heat (86° Pahr.) occur, one in Africa, and a smaller one in
the peninsula of India. In May and June the equator of
heat lies in India considerably north of the tropic, and the
two regions of excessive heat, becoming uni^d, extend unin-
terruptedly from North Africa, across Arabia and Persia, over
all India west of the Bay of Bengal. In July, a still hotter
area occurs in Nubia and Arabia, and Northern India is very
little inferior in temperature, whilst Southern India becomes
cooled; the heat throughout India being modified by the ac-
cession of the rains. In this mouth the isotherms in all parts
of Asia are much curved, the convexity being towards the*
north; and the amount of curve increases towards the north-
OTA part of the continent.
la August the equator of heat passes through Northern
India, which is still occupied by the rapidly contract ing region
of excessive heat. In September and October the equator of
heat advances rapidly towards the south, and in November
it has eutirely left India^-iuid corresponds almost exactly with
the terrestrial equator,- while the region of excessive heat lies
in the Indian Archipelago over Borneo and New Guinea.
We sec therefore tiiat from the vernal to the autumnal
eguiiiox a great part of India is preternatural ly hot, but that
from October to February (inclusive) it is comparatively cool,
and at tlic same time the continents of Africa and Australia
become preternaturally hot. During the summer months
therefore, or the hot season as it is commonly called in India,
the wind blows from the south towards the north, while in
the winter or cold scsusou it blows from north to K»utb. At
both HCOSOTW these directions oro often modified h\ local eutise.s,
hcsuk'rj hein^ uniformly allt-cted by the earth's rotation, and
by the heating mm cooling of the ooutmctit,
The monsoon* or periodical winds are known in the ladian
Oceun, JOH! indeed <<t,'uon<lly throughout TwJiiU !>y the name
of On* j-wwtlMve-t ?wd iKittU-eust mou*iv,,u, :^"v Using their